Adjustable pedal controller with obstruction detection

ABSTRACT

An adjustable control pedal for a motor vehicle includes an upper arm, a lower arm supported by the upper arm and operatively connected to the upper arm for selected movement relative to the upper arm, and a drive assembly operatively connected to the lower arm to selectively move the lower arm relative to the upper arm. A hall-effect sensor is located adjacent a drive screw and cooperates with a ring magnet rotatable with the drive screw to detect motion information. A controller receives the motion information and activates an electric motor upon initialization of the controller to move the lower pedal arm in a first direction until a first mechanical stop is engaged and establish a home stop position and to move the lower pedal arm in the other direction until a second mechanical stop is engaged and establish a travel stop position.

FIELD OF THE INVENTION

The present invention generally relates to improved adjustable pedalassemblies for motor vehicles and, more particularly, to control systemsfor adjusting control pedals to desired positions.

BACKGROUND OF THE INVENTION

Control pedals are typically provided in a motor vehicle, such as anautomobile, which are foot operated by the driver. Separate controlpedals are provided for operating brakes and an engine throttle. Whenthe motor vehicle has a manual transmission, a third control pedal isprovided for operating a transmission clutch. A front seat of the motorvehicle is typically mounted on tracks so that the seat is forwardly andrearwardly adjustable along the tracks to a plurality of positions sothat the driver can adjust the front seat to the most advantageousposition for working the control pedals.

This adjustment method of moving the front seat along the tracksgenerally fills the need to accommodate drivers of various size, but itraises several concerns. First, this adjustment method still may notaccommodate all drivers due to very wide differences in anatomicaldimensions of drivers. Second, the necessary position of the seat may beuncomfortable for some drivers. Therefore, it is desirable to have anadditional or alternate adjustment method to accommodate drivers ofvarious size.

Many proposals have been made to selectively adjust the position of thecontrol pedals relative to the steering wheel and the front seat inaddition to adjusting the front seat in order to accommodate drivers ofvarious size. These adjustable control pedals can actuate either a cablewhich is connected to an engine throttle, for example, or an electronicthrottle control (ETC) where an electric signal is sent to the enginethrottle which is proportional to the positioning of the pedal. Such“drive-by-wire” ETC pedals were adapted from fly-by-wire” aircraftpedals, and the ETC can be, for example, either a dual slopepotentiometer where the electric signal is proportional to rotation ofthe pedal, or a linear variable displacement transducer (LVDT) where theelectric signal is proportional to linear displacement of the pedal or acarrier operatively connected to the pedal. See, for example, U.S. Pat.No. 5,056,742 to Sakurai showing adjustable pedals which control brakesand rudders of a motor vehicle such as an aircraft. A mounting frame orcarrier is mounted in a base frame or support structure so that thecarrier can be adjusted forward or rearward by operation of a screwdevice or drive assembly. Pedals are pivotally connected directly to themulti-part carrier for pivotal movement relative to the carrier and aremoved to various adjusted positions with the forward/rearward movementof the carrier relative to the support structure. Transducers orgenerator means are mounted on the carrier and move with the carrier tothe various adjusted positions. These transducers have outputsresponsive to the pivotal movement of the pedals relative to the carrierwhich vary in magnitude in proportion to the extent of movement of thepedals relative to the carrier. It is readily apparent to those skilledin the art of adjustable control pedals that the pedals connected to thecarrier can have many different forms depending on the requirements ofthe particular motor vehicle such as, for example, in automobiles thepedal is typically in the form of a pedal arm extending from a pivotconnection to a lower end having a pad.

U.S. Pat. Nos. 5,632,183, 5,697,260, 5,722,302, 5,819,593, 5,937,707,and 5,964,125, the disclosures of which are expressly incorporatedherein in their entirety by reference, each disclose an example of anadjustable control pedal assembly. This control pedal assembly includesa hollow guide tube, a rotatable screw shaft coaxially extending withinthe guide tube, a nut in threaded engagement with the screw shaft andslidable within the guide tube, and a control pedal rigidly connected tothe nut. The control pedal is moved forward and rearward when anelectric motor rotates the screw shaft to translate the nut along thescrew shaft within the guide tube. While this control pedal assembly mayadequately adjust the position of the control pedal to accommodatedrivers of various size, this control pedal assembly is relativelycomplex and expensive to produce. The relatively high cost isparticularly due to the quantity of high-precision machined parts suchas, for example, the guide tube and due to the quantity of weldedjoints.

U.S. Pat. Nos. 3,643,525 and 3,643,524, the disclosures of which areexpressly incorporated herein in their entirety by reference, eachdisclose an example of an adjustable control pedal assembly which ismuch less expensive to produce. This control pedal assembly includes anupper arm having a single horizontal slot, a rotatable screw shaftattached to the upper arm and extending along the slot, a nut inthreaded engagement with the screw shaft and having a pin slidablewithin the slot, and a control pedal rigidly connected to the nut. Thecontrol pedal is moved forward and rearward when an electric motorrotates the screw shaft to translate the nut along the screw shaft.While this control pedal assembly may adequately adjust the position ofthe control pedal to accommodate drivers of various size and isrelatively inexpensive to produce, this control pedal is relativelyunstable and can have a relatively large amount of lash. That is,components of the control pedal are subject to vibration during regularoperation of the motor vehicle causing the components to rub or striketogether causing undesirable noise.

While these adjustable pedal systems may adequately adjust the positionof control pedals, these systems often do not know the exact location ofthe control pedal and/or can cause injury or damage when the controlpedals engage an obstruction. Accordingly, there is a need in the artfor an adjustable pedal assembly which selectively adjusts the positionof the control pedal to accommodate drivers of various size, isrelatively simple and inexpensive to produce, is able reset in order toidentify the exact position of the control pedal, is able to detect whenan obstruction is engaged during movement of the control pedal, and/oris highly reliable to operate.

SUMMARY OF THE INVENTION

The present invention provides an adjustable control pedal for a motorvehicle which overcomes at least some of the above-noted problems of therelated art. According to the present invention, an adjustable pedalassembly comprises, in combination, a carrier, a lower arm supported bythe carrier and operatively connected to the carrier for selectedmovement relative to the carrier, and a drive assembly operativelyconnected to the lower arm to selectively move the lower arm relative tothe carrier. The drive assembly comprises a drive screw connected to oneof the lower arm and the carrier, a drive nut connected to the other ofthe lower arm and the carrier and cooperating with the drive screw suchthat the drive nut travels along the drive screw upon rotation of thedrive screw, and an electric motor operatively connected to the drivescrew to selectively rotate the drive screw. A sensor is provided whichis adapted to detect motion information upon rotation of the drivescrew. A controller receives the motion information and is adapted toactivate the electric motor upon initialization of the controller tomove the lower arm in a first direction until a first mechanical stop isengaged and establish a home stop position and to move the lower arm inthe other direction opposite the first direction until a secondmechanical stop is engaged and establish a travel stop position. Thehome stop position and the travel stop position represent the mechanicallimits of travel for the lower arm.

According to another aspect of the present invention, an adjustablepedal assembly comprises, in combination, a carrier, a lower armsupported by the carrier and operatively connected to the carrier forselected movement relative to the carrier, and a drive assemblyoperatively connected to the lower arm to selectively move the lower armrelative to the carrier. The drive assembly comprises a drive screwconnected to one of the lower arm and the carrier, a drive nut connectedto the other of the lower arm and the carrier and cooperating with thedrive screw such that the drive nut travels along the drive screw uponrotation of the drive screw, and an electric motor operatively connectedto the drive screw to selectively rotate the drive screw. A sensor isprovided which is adapted to detect motion information upon rotation ofthe drive screw. A controller is adapted to selectively activate theelectric motor to move the lower arm, to receive the motion information,and to determine stall conditions of the lower arm based on the motioninformation during movement of the lower arm.

From the foregoing disclosure and the following more detaileddescription of various preferred embodiments it will be apparent tothose skilled in the art that the present invention provides asignificant advance in the technology and art of adjustable controlpedal assemblies. Particularly significant in this regard is thepotential the invention affords for providing a high quality,feature-rich, low cost assembly. Additional features and advantages ofvarious preferred embodiments will be better understood in view of thedetailed description provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further features of the present invention will be apparentwith reference to the following description and drawings, wherein:

FIG. 1 is a perspective view of an adjustable pedal assembly accordingto a preferred embodiment of the present invention;

FIG. 1A is a schematic view of the adjustable pedal assembly of FIG. 1;

FIG. 1B is a schematic end view of a hall-effect switch and ring magnetof FIG. 1A;

FIG. 1C is a graph showing output of the hall-effect sensor of FIG. 1Bover time;

FIG. 2 is a left side elevational view of a first adjustable controlpedal of the adjustable control pedal assembly of FIG. 1;

FIG. 3 is a rear elevational view of the first adjustable control pedalof FIG. 2;

FIG. 4 is an exploded elevational view of the adjustable control pedalof FIGS. 2 and 3;

FIG. 5 is an enlarged left perspective view of an upper portion of theadjustable control pedal of FIGS. 2 to 4;

FIG. 6 is an enlarged right side perspective view of an upper portion ofthe adjustable control pedal of FIGS. 2 to 5;

FIGS. 7A-C is a flowchart of a preferred initialization routine utilizedby the controller of the adjustable pedal assembly of FIG. 1;

FIGS. 8A-C is a flowchart of a preferred main program loop utilized bythe controller of the adjustable pedal assembly of FIG. 1;

FIGS. 9A-B is a flowchart of a preferred memory button routine utilizedby the controller of the adjustable pedal assembly of FIG. 1;

FIGS. 10A-B is a flowchart of a preferred find pedal hard stop routineutilized by the controller of the adjustable pedal assembly of FIG. 1;

FIGS. 11A-C is a flowchart of a preferred move pedal routine utilized bythe controller of the adjustable pedal assembly of FIG. 1;

FIGS. 12A-B is a flowchart which is a continuation of the preferred movepedal routine of FIGS. 11A-C; and

FIGS. 13A-B is a flowchart which is a continuation of the preferred movepedal routine of FIGS. 11A-C and 12A-B.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of an adjustable control pedalas disclosed herein, including, for example, specific dimensions,orientations, and shapes of the pedal arms and the slots will bedetermined in part by the particular intended application and useenvironment. Certain features of the illustrated embodiments have beenenlarged or distorted relative to others to facilitate visualization andclear understanding. In particular, thin features may be thickened, forexample, for clarity or illustration. All references to direction andposition, unless otherwise indicated, refer to the orientation of thecontrol pedal assembly illustrated in the drawings. In general, up orupward refers to an upward direction in the plane of the paper in FIGS.2 and 3 and down or downward refers to a downward direction in the planeof the paper in FIGS. 2 and 3. Also in general, fore or forward refersto a direction toward the front of the motor vehicle, that is, to theleft in the plane of the paper in FIG. 2 and aft or rearward refers to adirection toward the rear of the motor vehicle, that is, to the right inthe plane of the paper in FIG. 2.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

It will be apparent to those skilled in the art, that is, to those whohave knowledge or experience in this area of technology, that many usesand design variations are possible for the improved adjustable pedalassembly disclosed herein. The following detailed discussion of variousalternative and preferred embodiments will illustrate the generalprinciples of the invention with reference to an adjustable pedalassembly for use with a motor vehicle. Other embodiments suitable forother applications will be apparent to those skilled in the art giventhe benefit of this disclosure.

Referring now to the drawings, FIG. 1 shows an adjustable pedal assembly10 for a motor vehicle, such as an automobile, according to a preferredembodiment of the present invention which has control pedals selectivelyadjustable to desired forward/rearward positions by an operator ordriver of the motor vehicle. While the illustrated embodiments of thepresent invention are particularly adapted for use with an automobile,it is noted that the present invention can be utilized with any vehiclehaving at least one foot operated control pedal including trucks, buses,vans, recreational vehicles, earth moving equipment and the like, offroad vehicles such as dune buggies and the like, air borne vehicles, andwater borne vehicles.

As best shown in FIGS. 1 and 1A, the illustrated adjustable pedalassembly 10 includes first and second adjustable control pedals 12 a, 12b and a control system 14 for selectively adjusting the position of thecontrol pedals 12 a, 12 b. Typically, the control pedals 12 a, 12 b areadapted as brake and accelerator pedals respectively. While theillustrated adjustable pedal assembly 10 includes two control pedals 12a, 12 b, it is noted that the adjustable pedal assembly 10 can have asingle control pedal within the scope of the present invention such as,for example, a single control pedal adapted as a clutch, brake oraccelerator pedal. It is also noted that the adjustable pedal assembly10 can have more than two control pedals 12 within the scope of thepresent invention such as, for example, three control pedals adapted asclutch, brake and accelerator pedals. The control pedals 12 a, 12 b areselectively adjustable by the motor vehicle operator in aforward/rearward direction as described in more detail hereinafter. Inmultiple control pedal embodiments, the control pedals 10 are preferablyadjusted together simultaneously to maintain desired relationshipsbetween the control pedals such as, for example, “step over”, that is,the forward position of the accelerator pedal 12 b relative to the brakepedal, 12 a and “pedal angles”, that is, the orientation of the contactsurfaces of the pedal pads. It is noted however, that individualadjustment of a single control pedal 12 a, 12 b is within the scope ofthe present invention.

While only the first control pedal 12 a, which is adapted as a brakepedal, is described in detail hereinbelow, the second control pedal 12b, which is adapted as an accelerator pedal, is generally the sameexcept as noted herein and as apparent to those skilled in the art giventhe benefit of this disclosure. For a detailed description of othersuitable adjustable control pedals 12 a, 12 b adapted as both brake andaccelerator pedals, see, for example, U.S. patent application Ser. No.564,355, the disclosure of which is expressly incorporated herein in itsentirety by reference.

As best shown in FIGS. 2-6, the first control pedal 12 a includes anupper pedal arm or carrier 16 having first and second plates or members18, 20, a lower pedal arm 22 supported by the upper pedal arm 16 andcarrying a pad or pedal 24 for engagement by the foot of the motorvehicle operator, and a drive assembly 26 for moving of the lower pedalarm 22 relative to the upper pedal arm 16 to adjust the forward/rearwardposition of the pedal 24. The upper pedal arm 16 is sized and shaped forpivotal attachment to a mounting bracket 28. The mounting bracket 28 isadapted to rigidly attach the adjustable control pedal 12 to a firewallor other rigid structure of the motor vehicle in a known manner. Theupper pedal arm 16 is adapted for pivotal attachment to the mountingbracket 28. The illustrated first and second members 18, 20 of the upperpedal arm 16 each have an opening 30 formed for cooperation with themounting bracket 28 and an axle or pivot pin 32. With the pivot pin 32extending through the mounting bracket 28 and the openings 30 of thefirst and second members 18, 20, the upper pedal arm 16 is pivotablerelative to the fixed mounting bracket 28 about a horizontally andlaterally extending pivot axis 34 formed by the central axis of thepivot pin 32. A spacer 36 is preferably provided about the pivot pin 32between the first and second members 18, 20 to maintain a desireddistance between the first and second members 18, 20. The illustratedfirst and second members 18, 20 of the upper pedal arm 16 aresubstantially identical and are rigidly connected together to pivottogether about the pivot pin 32 in unison.

The lower portion of the first and second members 18, 20 is adapted forsupporting the lower pedal arm 22 and for selected fore and aft movementof the lower pedal arm 22 relative to the first and second members 18,20 along the lower portion as described in more detail hereinafter. Theillustrated lower portion has a pair of vertically spaced apart elongateopenings or slots 38, 40 formed therein which generally extend in aforward/rearward direction along the length of the lower portion. Theillustrated slots 38, 40 are each substantially straight. Preferably,the drive or lower slot 40 is offset rearward of the guide or upper slot38 but overlapping the upper slot 38. The lower portion is substantiallyplanar or flat at least in the areas adjacent the slots 38, 40 and theslots 38, 40 are open laterally through the entire thickness of thefirst and second members 18, 20. The slots 38, 40 are sized and shapedfor cooperation with the lower pedal arm 22 for substantially linearforward/rearward movement of the pedal 24 relative the upper pedal arm16 over a desired adjustment range, such as about three inches, asdescribed in more detail hereinbelow. It is noted that the separateupper and lower slots 38, 40 can alternatively be separate portions of asingle slot such as a “C-shaped”, “S-shaped”, or other nonlinear slot.

The upper pedal arm 16 is operatively connected to a control device suchas a clutch, brake or throttle such that pivotal movement of the upperpedal arm 16 about the pivot axis 34 operates the control device in adesired manner. The upper pedal arm 16 can be connected to the controldevice by, for example, a push-pull or Bowden cable for mechanicalactuation or by a sensor or electrical wire or cable for electronicactuation. The illustrated upper pedal arm 16 is provided with a boosterpin 42 for connection to the control device by a mechanical actuator.The illustrated upper pedal arm 16 is also provided with a switch pin 44for connection to a switch for indicator lights such as brake lights sothat the indicator lights indicate actuation of the pedal, that is,pivotal movement about the pivot axis 34, of the control pedal 12 by theoperator.

The upper and lower pedal arms 16, 22 are preferably formed of asuitable metal such as steel but one or both can alternatively be formedof other suitable materials such as, for example, plastics like NYLON,aluminum, or magnesium. The illustrated lower pedal arm 22 is formed ofan elongate plate oriented in a vertical plane substantially parallel toplanes of the first and second members 18, 20. The upper end of thelower pedal arm 22 is adapted for movement relative to the upper pedalarm 16 between first and second members 18, 20 and along the upper andlower slots 38, 40. The upper end of the lower pedal arm 22 is providedwith upper and lower guide pins or blocks 48, 50 laterally andhorizontally extending therefrom to cooperate with the slots 38, 40 ofthe first and second members 18, 20 to form four sliding pin-and-slotconnections for linearly moving the lower pedal arm 22 relative to theupper pedal arm 16. The lower end of the lower pedal arm 22 is sized andshaped to carry the rearward-facing pedal 24. The pedal 24 is adaptedfor depression by the driver of the motor vehicle to pivot the controlpedal 12 about the pivot axis 34 to obtain a desired control input tothe motor vehicle through the movement of the booster pin 42. It isreadily apparent to those skilled in the art that the pedal arm 22 canbe comprised of plastic or metal, and that the pedal arm 22 can be ofunitary construction with the pedal or pad 24 or, alternatively, canhave a pad support at its lower end to receive the pedal or pad 24 sothat the pad 24 can be comprised of rubber or other suitable materialfor foot comfort.

Bushings 52 preferably encircle end portions of the guide pins 48, 50and extend within the slots 38, 40. The bushings 52 are sized and shapedto closely conform with the guide pins 48, 50, particularly at theengagement surfaces contacting the edges of the slots 38, 40. The guidepins 48, 50 and the bushings 52 are sized and shaped so that there isvery little or no vertical movement or “play” for the guide pins 48, 50within the slots 38, 48. Flanges of the bushings 52 are preferably sizedto extend between the lower pedal arm 22 and the first and secondmembers 18, 20 so that there is very little or no lateral movement or“play” for the lower pedal arm 22 between the first and second members18, 20. The bushings 52 are preferably formed of a suitable plastic orpolymer material but can alternatively be any other type of suitablewear resistant and/or low friction material.

The drive assembly 26 includes a screw shaft or drive screw 54, a drivescrew attachment or housing 56 for securing the drive screw 54 to theupper pedal arm 16, a drive nut 58 adapted for movement along the drivescrew 54 in response to rotation of the drive screw 54, an electricmotor 60 for rotating the drive screw 54, and a drive cable 62 foroperatively connecting the electric motor 60 to the drive screw 54 andtransmitting rotational motion and torque thereto.

The drive screw 54 is an elongate shaft having a threaded portionadapted for cooperation with the drive nut 58. The drive screw 54 ispreferably formed of metal such as, for example, steel but can bealternately formed of a plastic resin such as, for example, NYLON. Theforward end of the drive screw 54 is journaled by the drive screwhousing 56 for rotation of the drive screw 54 about its longitudinalaxis by the electric motor 60. The drive screw 54 rearwardly extendsfrom the drive screw housing 56 generally parallel to and adjacent thelower slots 38 in the first and second members 18, 20 in a cantileveredfashion. Mounted in this manner, the drive screw 54 is generallyhorizontal. The illustrated drive screw 54 is provided with a bushing 64for connection to the housing 56 to form a relatively fixed rotatingjoint. The drive screw 56 can alternatively be connected to the drivescrew housing 56 with a self-aligning or freely pivoting rotating joint,that is, a joint which freely permits pivoting of the drive screw 54relative to the drive screw housing 56 and the first and second members18, 20 about at least axes perpendicular to the drive screw rotationalaxis 66. The self-aligning joint automatically corrects misalignment ofthe drive screw 54 and/or the drive nut 58. The self-aligning joint alsoallows the lower slot 40 to be nonlinear when desired. The self aligningjoint can be, for example, a ball/socket type joint.

The drive screw housing 56 is sized and shaped for supporting theforward end of the drive screw 54 and attaching the drive screw 54 tothe first and second members 18, 20. The drive screw housing 56 ispreferably molded of a suitable plastic material such as, for example,NYLON but can alternatively be formed of metal such as steel. Theillustrated drive-screw housing 56 is secured to the upper pedal arm 16with a snap-fit connection. It is noted, however, that the drive screwhousing 56 can be secured to the upper pedal arm 16 in other suitablemanners such as, for example, welding, staking, or mechanical fasteners.

The drive nut 58 is adapted for axial movement along the drive screw 54in response to rotation of the drive screw 54. The drive nut 58 ispreferably molded of a suitable plastic material such as, for example,NYLON but can alternatively be formed of metal such as, for examplesteel. The illustrated drive nut 58 is rigidly secured to the lowerguide pin 50. The lower guide pin 50 can be alternatively connected tothe drive nut 58 with a self-aligning or freely pivoting joint, that is,a joint which freely permits pivoting of the drive nut 58 relative tothe lower guide pin 50 about at least axes perpendicular to therotational axis 66 of the drive screw 54. The self-aligning jointautomatically corrects misalignment of the drive nut 58 and/or the drivescrew 54. The self aligning joint can be, for example, a ball/sockettype joint.

The electric motor 60 can be of any suitable type and can be secured tothe firewall or other suitable location such as, for example, themounting bracket 28. The drive cable 62 is preferably a flexiblepush-pull-type or Bowden cable and connects the output shaft of theelectric motor 60 and the forward end of the drive screw 54 so thatrotation of the electric motor 60 rotates the drive screw 54. It isnoted that the drive screw 54 and the electric motor 60 can bealternatively connected with a rigid connection. It is noted thatsuitable gearing 68 is provided between the electric motor 60 and thedrive screw 54 as necessary depending on the requirements of theadjustable pedal assembly 10. It is also noted that the fixed portion orsheath of the drive cable 62 is rigidly secured to the forward end ofthe drive screw housing 56 and a rotating portion or core of the drivecable 62 is operatively connected to the forward end of the drive screw54 to rotate the drive screw 54 therewith. See U.S. patent applicationSer. No. 09/492,238, the disclosure of which is expressly incorporatedherein in its entirety by reference, for a more detailed description ofa suitable drive screw, housing, and/or cable support. Also see U.S.patent application Ser. No. 09/642,975, the disclosure of which isexpressly incorporated herein in its entirety by reference, for a moredetailed description of the control pedal 12.

As best shown in FIG. 1, the control system 14 preferably includes acentral processing unit (CPU) or controller 70 for operating theelectric motor 60, an operator interface 72 for exchanging informationbetween the driver and the controller 70, and at least one sensor 74 fordetecting motion of the control pedals 12 a, 12 b and providing suchmotion information to the controller 70. The control system 14 forms acontrol loop wherein the controller 70 selectively activates anddeactivates the electric motor 60. When activated, the electric motor 60rotates the drive screws 54 through the drive cables 62. It is notedthat while the drive screws 54 of the illustrated embodiment areconnected to the electric motor 60 in parallel, they can alternativelybe connected to the electric motor 60 in series. The sensor or sensors74 detect movement of the control pedals 12 a, 12 b and send(s) signalsto the controller 70 which enables the controller 70 to deactivate theelectric motor 60 when movement to a desired position has been obtained.

The controller 70 includes processing means and memory means which areadapted to control operation of the adjustable pedal assembly 10 asdescribed in detail herein. The controller 70 is preferably incommunication with a motor vehicle control unit 76 through a local bus78 of the motor vehicle or a direct connection so that motor vehicleinformation, such as ignition switch information, can be supplied to orexamined by the controller 70 and status of the adjustable pedalassembly 10 can be supplied to or examined by the motor vehicle controlunit 76. It is noted that while illustrated control system 14 utilizes adedicated controller 70, the controller can alternatively be the motorvehicle control unit 76 or a controller of another system of the motorvehicle such as, for example, a keyless entry system or a powered seatsystem.

The illustrated operator interface 72 includes a forward button orswitch 80, a reverse or rearward button or switch 82, an indicatordevice 84, and first and second memory buttons or switches 86, 88. Whenactivated, the forward switch 80 sends control signals to the controller70 to move the control pedals 12 a, 12 b in a forward direction. Whenactivated, the reverse switch 82 sends control signals to the controller70 to move the control pedals 12 a, 12 b in a rearward direction. Theillustrated forward and rearward switches 80, 82 are a singlerocker-type switch but can be other types of suitable switches such as,for example, push-button switches or toggle switches. The illustratedindicator device 84 is an indicator or status light such as an LED whichis selectively illuminated to convey information to the operator. It isnoted that the indicator device 84 can alternatively be other suitabletypes of devices which can convey information such as, for example, anLED or LCD display. When activated, the memory switches 86, 88 sendcontrol signals to the controller 70 to move the control pedals 12 a, 12b to preferred locations previously saved in memory of the controller70. Preferably, when activated and held for a predetermined period oftime, such as about two seconds, the controller 70 saves the currentposition in memory so that subsequent actuation of that memory switch86, 88 will send a control signal to the controller 70 to move thecontrol pedals 12 a, 12 b to the current location. Preferably, theindicator device 84 acknowledges the saving of the current position byfor example, blinking the indicator light for a predetermined period oftime. The illustrated memory switches 86, 88 are a single push-buttonswitches but can be other types of suitable switches such as, forexample, toggle switches. It is noted that the operator interface 72 canalso include other control switches when desired such as, for example, alock out button or switch which when activated sends control signals todeactivate the system and prevent movement of the control pedals 12 a,12 b and/or an override button or switch which when activated permitsthe control pedals 12 a, 12 b to be moved by the driver in a desiredmanner regardless of existing conditions.

The illustrated embodiment provides each control pedal 12 a, 12 b with asensor 74 to detect movement of the control pedals 12 a, 12 b and sendsignals relating to such movement information to the controller 70.Alternatively, a single sensor 74 or more than two sensors 74 can beutilized. The illustrated sensors 74 are located adjacent the drivescrews 54 and are adapted provide movement information, in the form ofdistance and speed information, to the controller 70. The sensors 74 arepreferably hall-effect switches mounted adjacent ring magnets 90. Asbest shown in FIG. 1B, each ring magnet 90 comprises a predeterminednumber of north and south poles such as, for example, a total of about24 to 34 north and south poles. It is noted, however, that a ring magnetwith any number of poles can be used. The ring magnet 90 is mounted forrotation with the drive screw 54 so that the predetermined number ofmagnet poles pass the sensor 74 each revolution of the drive screw 54.During rotation of the drive screw 54, the sensor 74 provides a squarewave pulse stream to the controller 70. As best shown in FIG. 1C, thewidth of each pulse indicates the time one type of magnet pole wasadjacent the sensor 74 and the width between pulses indicates the timethe other type of magnet pole was adjacent the sensor. Therefore, widthof the pulses and width between pulses proportionally decreases asrotational velocity of the drive screw 54 increases. Speed can bedetermined by pulse width, width between pulses, or preferably by bothpulse width and width between pulses. The distance the drive nut 58, andthus the lower pedal arm 22, travels with each rotation of the drivescrew 54 is preprogrammed in the controller 70. Therefore, thecontroller 70 can determine both the location and speed of the lowerpedal arms 22 from the movement information received from the sensors74. This motion information is used by the controller 70 in many ways asdescribed in detail hereinbelow.

It is noted that other suitable sensors can be alternatively utilizedsuch as, for example, a potentiometer. The sensors 74 can alternativelybe position sensors such as, for example, a linear hall-effect sensorand/or a linear potentiometer. The sensors 74 can also alternatively bea current shunt on the electric motor 60 providing motor commutatorpulses to detect position or motor current. Therefore, it is noted thatthe sensors 74 can alternatively have other locations such as, forexample, between the upper and lower pedal arms 16, 22 and/or at theelectric motor 60. Other motion information sensors 74 and locations forthe sensors 74 will be apparent to those skilled in the art given thebenefit of this disclosure.

The motion information from the sensors 74 can be utilized toautomatically stop the control pedals 12 a, 12 b at ends of travel alongthe drive screw 54. The controller 70 is preferably adapted to stop themotor 60 when motion information indicates that the drive nut 58 hasreached a predetermined end of travel along the drive screw 54 prior toengaging a “hard” or mechanical stop or abutment. The position of the“soft” or electronic stop points relative to the hard stop points at theend of travel are preferably preprogrammed or determined by thecontroller 70. When the controller 70 determines that the control pedals12 a, 12 b have reached the soft or electronic stop points, thecontroller 70 stops the motor 60 and thus movement of the drive nuts 58along the drive screws 54. Fore-aft movement of the lower pedal arms 16,therefore, is electronically stopped without engaging mechanical stopsand resulting stress on the motor 60 and mechanical components. When ahard stop is engaged, the motor 60 stalls and current increases whichmay cause overheating of the motor 60 and a resulting shortened life ofthe motor 60. It is noted, however, that the adjustable pedal assembly10 is preferably provided with hard stops for limiting travel of thedrive nuts 58 beyond the soft stops for use in initializing or resettingthe system 14 an use in the event of a failure of the soft stops. In theillustrated embodiment, the hard stops include the ends of the upper andlower slot 38, 40 which form abutments which are engaged by the upperand lower guide pins 48, 50 at the end of travel along the slots 38, 40to limit fore-aft movement of the lower arms 16 and axial movement ofthe drive nuts 58.

The motion information from the sensors 74 can be utilized by thecontroller 70 to move the control pedals 12 a, 12 b to desiredpositions. Because each pulse of the sensor output indicates apredetermined distance traveled, the total number of pulses indicatesthe total distance traveled. Therefore, by setting a home position atzero pulses, every other position along the travel length can be definedby a number of pulses from the home position. The current positiontherefore can be identified by the controller 70 which keeps track ofthe cumulative effect of all of the pulses which have occurred sincetraveling from the home position. In the illustrated embodiment, thehome or forward soft stop is set as zero pulses and the travel orrearward soft stop is set as the total number of pulses from the homesoft stop. In this manner, the current position can be stored by storingthe number of pulses that the current position is away from the homeposition.

The motion information from the sensors 74 can be utilized to detect anobstruction in the path of at least one of the control pedals 12 a, 12 bsuch as, for example, the operator's foot. A potential “pinch” situationis detected if signals from the sensors 74 to the controller 70 indicatethat there is a stall condition, by change in speed, acceleration or thelike, which indicates that an obstruction has been engaged by at leastone of the control pedals 12 a, 12 b. If the sensors 74 detect a stallor obstruction, the controller 70 automatically stops the motor 60and/or reverses direction of the movement for a predetermined distanceor to the previous position to prevent injury to a person or damage toan object or the adjustable pedal assembly 10. If the sensors 74indicate a second obstruction upon reversing direction, the controller70 places the system in fault mode. Preferably the indicator device 84identifies that the system 14 is in fault mode such as, for example, byblinking the indicator light.

Because each pulse width is a function of time (the width is the time totravel a predetermined distance), the pulse widths or velocityinformation can be utilized to detect a stalled or obstructioncondition. In the illustrated embodiment, after a predetermined startupperiod which permits the system to reach full speed, such as about 6 toabout 8 pulses, a time or pulse width is stored indicating a full speedpulse. The full speed pulse is determined each motion cycle to reducethe effect of long term degradations. During movement, each pulse widthis compared to the stored full speed pulse width to determine if astalled condition is beginning to take place. Preferably, an averagingalgorithm is utilized wherein each pulse width (or some derivative ofeach pulse width) is compared to the sum of the stored full speed pulsewidth and a constant value. The constant value can be a fixedpercentage, such as 50%, of the saved full speed pulse width. The fixedpercentage is dependant on variables of the mechanical system and can befrom about 10% to about 300%. Accordingly, each system must be tested todetermine the optimum fixed percentage. If a measured pulse width isgreater than the sum of the stored full speed pulse width and theconstant value, there is an indication of a stall condition arising.Typically, more than one pulse width should indicate a stall conditionarising before acting on the stalled condition depending on the desiredsensitivity of the system 14.

The motion information from the sensors 74 can be utilized to return thecontrol pedals 12 a, 12 b to a stored preferred location (a storednumber of pulses from the home position) when selected by the driver.The driver adjusts the control pedals 12 a, 12 b to a preferred locationand engages one of the memory switches 86, 88 for a predetermined periodof time which is preferably verified by the indicator device 84, such asby a flash of the indicator light, so that the preferred location issaved in memory. At a later time, when the driver engages the samememory switch 86, 88 the controller 70 automatically activates the motor60 to rotate the drive screws 54 and move the control pedals 12 a, 12 bfrom the current position (a known number of pulses from the homeposition) to the saved position (a stored number of pulses from the homeposition). The controller 70 automatically stops the motor 60 when themotion information from the sensors 74 that the necessary number ofpulses, in the necessary direction, have occurred to reach the storedposition.

Each control pedal 12 a, 12 b preferably includes a separate sensor 74so that motion information is obtained regarding each of the drivescrews 54. By having motion information regarding each drive screw 54,the controller 70 can identify when the control pedals 12 a, 12 b, arenot moving in the same manner, that is maintaining the same relationshipto each other. Preferably, the controller 70 deactivates the motor 60 ifthere is an indication that a predetermined relationship between two ormore of the control pedals 12 a, 12 b is not maintained. For example,the predetermined relationship can be the step over of the brake andaccelerator pedals. If the sensors 74 indicate a change in relationshipbetween the control pedals 12 a, 12 b, the controller 70 places thesystem in fault mode. Preferably the indicator device 84 identifies thatthe system 14 is in fault mode such as, for example, by blinking theindicator light.

The controller 70 is preferably adapted to selectively trigger aninitialization process to identify where the control pedals 12 a, 12 bare located. This initialization process can be utilized at start upafter any loss of power, such as a battery change, and/or after a systemshut down due to failure detection or fault mode. When theinitialization process is triggered, the controller 70 activates themotor 60 to move the drive nuts 58 forward until they reach the forwardor home hard stop. The controller 70 then reverses the motor 60 to movethe drive nuts 58 in a rearward direction until they reach the rearwardor travel hard stop. The controller 70 compares the distance between thelocated hard stops, or alternatively the determined soft stops, todetermine if an artificial hard stop or obstruction was engaged. If thedistance is adequate, the controller 70 sets the soft stops apredetermined distance from the located hard stops. If the distance isnot adequate, that is it indicates an obstruction was engaged, thecontroller 70 places the system in fault mode. Preferably the indicatordevice 84 identifies that the system 14 is in fault mode such as, forexample, blinking the indicator light.

It is noted that the LED can blink at different rates depending on thetype of failure such as, for example, a one second rate for a step overfailure, a two second rate for an initialization failure, a 0.25 secondrate for a temporary fault in the circuit such as an H-bridge.Preferably, means are provided for resetting or initializing the system14 when in fault mode such as, for example, a reset switch. In thepreferred embodiment, the reset or initialization process is triggeredby engaging the forward switch 80 and each of the memory switches 86, 88simultaneously.

FIGS. 7A-13B illustrate flow charts for preferred operation of thecontroller 70. The initialization program loop or routine is best shownin FIGS. 7A-C. The controller 70 runs a “find pedal hard stops routine”when the initialization process is triggered. The find pedal hard stopsroutine is described in more detail hereinbelow with regard to FIG. 10.If the hard stops are not found, the system 14 is placed in fault modeand the LED light 84 is blinked at a predetermined rate such as twoseconds on and two seconds off. If the hard stops are found, the softstops are then determined by the controller 70. Preferably, the homesoft stop location is determined by adding a predetermined distance(predetermined number of pulses) from the home hard stop. The travelsoft stop is determined by subtracting the home soft stop location(number of pulses from the home hard stop) from the from the travel hardstop location (number of pulses from the home hard stop). The distancebetween the travel and home soft spots is compared to a predetermineddistance to determine if an artificial hard stop or obstacle wasengaged. If an obstacle was engaged, the system 14 is placed in faultmode and the LED light 84 is blinked at a predetermined rate such as twoseconds on and two seconds off. If an obstacle was not engaged, storedmemory positions for the memory switches 86, 88 are set to the home softstop and the control pedals 12 a, 12 b are moved between the travel softstop and the home soft stop. If a stall or obstruction is detectedduring this movement, the system 14 is placed in fault mode and the LEDlight 84 is blinked at a predetermined rate, such as two seconds on andtwo seconds off. If a stall or obstruction is not detected during thismovement, the two pedal positions are set equal and the main programloop is initiated.

The main program loop is best shown in FIGS. 8A-C. When an ignitionswitch of the motor vehicle is detected to be off, the controller 70checks for a step over fault condition (the two control pedals are nolonger at equal positions). If a step over fault condition isdetermined, the system 14 is placed in fault and the LED light 84 isblinked at a predetermined rate such as one second on and one secondoff. If the user attempts to reset the system 14, the initializationprocess of FIGS. 7A-C is initiated. If a step over fault condition isnot detected, the controller 70 checks for an H-bridge or circuit faultcondition. If a circuit fault condition is determined, the system 14 isplaced in fault and the LED light 84 is blinked at a predetermined ratesuch as a quarter of a second on and a quarter of a second off. Thecontroller 70 continues to check if the condition remains and clears thefault state when the condition no longer exists. If a circuit faultcondition is not detected and the forward switch 80 or the rearwardswitch 82 is pressed for at least a predetermined period of time, suchas more than ten milliseconds, the move pedal routine (FIGS. 11A-C) isinitiated after properly setting the direction to forward or rearwarddepending on which direction switch 80, 82 was pressed. If a circuitfault condition is not detected and the first memory switch 86 or thesecond memory switch 88 is pressed for at least a predetermined periodof time, such as more than ten milliseconds, the memory button routine(FIGS. 9A-B) is initiated after properly setting the button number to 1or 2 depending on which memory switch 86, 88 was pressed. Aftercompleting the memory routine, the move pedal routine is initiated.

The memory button program loop or routine is best shown in FIGS. 9A-B.If the memory switch 86, 88 is released prior to a predetermined periodof time, such as two seconds, memory movement is enabled. The controller70 determines the difference between the current pedal position and thedesired memory position (number of pulses). If the current pedalposition is greater than the memory position, the movement direction isset to forward and the move pedal routine is initiated. If the currentpedal position is less than the memory position, the movement directionis set to rearward and the move pedal routine is initiated. If thememory switch 86, 88 is not released prior to the predetermined periodof time, such as two seconds, the current pedal position (number ofpulses from the home position) is saved into the memory position of thememory switch 86, 88 that was pressed by the operator and the LED 84 isblinked for a predetermined period of time such as 250 milliseconds.

The find pedal hard stop program loop or routine is best shown in FIGS.10A-B. Initially, the movement set point, that is the current position,is set to zero and the movement direction is set to forward. The movepedal routine is initiated to move the control pedals 12 a, 12 b in theforward direction for a number of pulses which ensures that the forwardhard stop will be engaged. When a stall is detected, the two pedalpositions are set to zero because they are at the home hard stop. Themovement direction is set to rearward and the move pedal routine isinitiated to move the control pedals 12 a, 12 b in the rearwarddirection for a number of pulses which ensures that the rearward hardstop will be engaged. When a stall is detected, the travel hard stop isset and the controller 70 returns to the initialization routine.

The move pedal program loop or routine is best shown in FIGS. 11A-13B.Initially, previous and saved pulse width counts are set to zero. Thehall-effect sensor 74 of the first control pedal 12 a is monitored todetermine the state of the sensor pulses (high or low). Each time thereis a transition in output from the sensor 74, from either low to high orhigh to low, the pulse count indicating the current position of thefirst pedal 12 a is incremented or decremented depending on thedirection of travel. The hall-effect sensor 74 of the second controlpedal 12 b is monitored in the same manner. With the pulse countsindicating the current position of each of the control pedals 12 a, 12 bbeing continuously updated, the controller 70 can determine whether thepulse count indicating the current position is equal to the set pointindicating a desired position. When a set point is reached, the movementis complete.

During the move pedal routine, the controller 70 continuously checks forvarious conditions which indicate movement should be stopped. Forexample, the controller 70 determines if the home soft stop has beenreached if travelling in the forward direction and if the travel softstop has been reached in travelling in the rearward direction. If a softstop is reached, movement is complete. The controller 70 also determinesif a stall condition is present. If a stall condition is detected,movement is stopped and/or reversed. The controller 70 furtherdetermines if there is a step over error, that is the first and secondcontrol pedals 12 a, 12 b are not in the same current position. If thereis a step-over error, movement is complete. The move routine continuesto loop until the movement is complete or the direction switch 80, 82 isreleased by the operator and the controller stops the motor 60.

During movement of the control pedals 12 a, 12 b, rotation of the motor60 rotates the drive screw 54 through the drive cable 62 and causes thedrive nut 58 to axially move along the drive screw 54 in the desireddirection. The drive nut 58 moves along the drive screw 54 because thedrive nut 58 is held against rotation with the drive screw 54 by thelower guide pin 50. As the drive nut 58 axially moves along the drivescrew 54, the lower guide pin 50 moves along the lower slots 40 becausethe lower guide pin 50 is secured to the drive nut 58. It is noted thatbinding of the drive nut 58 along the drive screw 54 is minimized if aself-aligning joint is provided, between the drive screw 54 and thedrive screw housing 56 and/or the drive nut 58 and the lower guide pin50, to automatically align the components so that the drive nut 58 cansmoothly travel along the drive screw 54. As the lower guide pin 50slidingly moves along the lower slots 40, the lower pedal arm 22 ismoved therewith to adjust the forward/rearward position of the pedal 24.As the lower pedal arm 22 moves, the upper guide pin 48 slides along theupper slots 38. With such movement, the pedal 24 travels in asubstantially linear and horizontal path, that is, the pedal 24 moves ina forward/rearward direction and generally remains at the same heightrelative to the fixed mounting bracket 28 and the upper pedal arm 16which does not move relative the mounting bracket 28 during adjustmentof the pedal 24. The lower pedal arm 22 pivots as it moves so that theorientation of the pedal 24 slightly changes. This change in orientationof the pedal 24 is typically too small to be detected by the motorvehicle operator. As the position of the pedal 24 is adjusted byrotating the drive screw 54, the upper pedal arm 16 remains in fixedposition relative to the mounting bracket 28. It can be seen from theabove description that activation of the motor 60 changes the positionof the lower pedal arm 22 relative to the upper pedal arm 16 and theposition of the pedal 24 relative to the motor vehicle operator but notthe position of the upper pedal arm 16 relative to the mounting bracket28 and therefore does not affect the connection of the upper pedal arm16 to the control device of the motor vehicle through the booster pin42.

From the foregoing disclosure and detailed description of certainpreferred embodiments, it is also apparent that various modifications,additions and other alternative embodiments are possible withoutdeparting from the true scope and spirit of the present invention. Forexample, it is apparent to those skilled in the art, given the benefitof the present disclosure, that the sensors 74 can have many differentforms, quantities, and locations. The embodiments discussed were chosenand described to provide the best illustration of the principles of thepresent invention and its practical application to thereby enable one ofordinary skill in the art to utilize the invention in variousembodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the present invention as determined by the appendedclaims when interpreted in accordance with the benefit to which they arefairly, legally, and equitably entitled.

What is claimed is:
 1. An adjustable pedal assembly comprising, incombination: a carrier; a lower arm supported by the carrier andoperatively connected to the carrier for selected movement relative tothe carrier; a drive assembly operatively connected to the lower arm toselectively move the lower arm relative to the carrier, the driveassembly comprising a drive screw connected to one of the lower arm andthe carrier, a drive nut connected to the other of the lower arm and thecarrier and cooperating with the drive screw such that the drive nuttravels along the drive screw upon rotation of the drive screw to movethe lower arm, and an electric motor operatively connected to the drivescrew to selectively rotate the drive screw; a sensor positioned todetect motion information indicating movement of the lower arm uponrotation of the drive screw; and a controller connected to the motor toselectively activate and deactivate the motor and connected to thesensor to receive the motion information from the sensor, the controllerhaving a processor programmed to activate the electric motor uponinitialization of the controller to move the lower arm in a firstdirection until a first mechanical stop is engaged and establish a homestop position and to reverse direction of the electric motor uponengaging the first mechanical stop to move the lower arm in the otherdirection opposite the first direction until a second mechanical stop isengaged and establish a travel stop position, wherein the home stopposition and the travel stop position represent the mechanical limits oftravel for the lower arm.
 2. The adjustable pedal assembly according toclaim 1, wherein the processor is programmed to determine electroniclimits of travel for the lower arm based on the mechanical limits oftravel to reduce engagement with the first and second mechanical stopsduring movement of the lower arm.
 3. The adjustable pedal assemblyaccording to claim 2, wherein the controller compares a distance betweenthe electronic limits of travel with a predetermined distance todetermine if an undesired obstacle was engaged when determining the homestop position and the travel stop position.
 4. The adjustable pedalassembly according to claim 1, wherein the motion information includesdistance information.
 5. The adjustable pedal assembly according toclaim 4, wherein the motion information includes velocity informationand the processor is programmed to determine a stall condition based onthe velocity information during movement of the lower arm.
 6. Theadjustable pedal assembly according to claim 1, wherein the sensor isone of a hall-effect switch, a potentiometer, a linear hall-effectdevice, a linear potentiometer, and a current shunt.
 7. The adjustablepedal assembly according to claim 1, wherein the sensor is locatedadjacent the drive screw.
 8. The adjustable pedal assembly according toclaim 7, wherein the sensor is a hall-effect switch cooperating with aring magnet rotatable with the drive screw.
 9. The adjustable pedalassembly according to claim 1, further comprising: a second carrier; asecond lower arm supported by the second carrier and operativelyconnected to the second carrier for selected movement relative to thesecond carrier; wherein the drive assembly is operatively connected tothe second lower arm to selectively move the second lower arm relativeto the second carrier, the drive assembly comprises a second drive screwconnected to one of the second lower arm and the second carrier, asecond drive nut connected to the other of the second lower arm and thesecond carrier and cooperating with the second drive screw such that thesecond drive nut travels along the second drive screw upon rotation ofthe second drive screw to move the second lower arm, and the electricmotor is operatively connected to the second drive screw to selectivelyrotate the second drive screw; a second sensor positioned to detectmotion information indicating movement of the second arm upon rotationof the second drive screw; and wherein the controller is connected tothe second sensor to receive the motion information from the secondsensor and the processor is programmed to activate the electric motorupon initialization of the controller to move both the first and secondlower arms.
 10. The adjustable pedal assembly according to claim 1,wherein the controller determines a total travel length afterdetermining the home stop position and the travel stop position.
 11. Anadjustable pedal assembly comprising, in combination: an upper arm; alower arm supported by the upper arm and operatively connected to theupper arm for selected movement relative to the upper arm; a driveassembly operatively connected to the lower arm to selectively move thelower arm relative to the upper arm, the drive assembly comprising adrive screw connected to one of the upper and lower arms, a drive nutconnected to the other of the upper and lower arms and cooperating withthe drive screw such that the drive nut travels along the drive screwupon rotation of the drive screw to move the lower arm, and an electricmotor operatively connected to the drive screw to selectively rotate thedrive screw; a sensor positioned to detect motion information indicatingmovement of the lower arm upon rotation of the drive screw, the motioninformation including distance information and velocity information; anda controller connected to the motor to selectively activate anddeactivate the motor and to the sensor to receive the motion informationfrom the sensor, the controller having a processor programmed toactivate the electric motor upon initialization of the controller tomove the lower arm in a first direction until a first mechanical stop isengaged and establish a home stop position and to reverse direction ofthe electric motor upon engaging the first mechanical stop to move thelower arm in the other direction opposite the first direction until asecond mechanical stop is engaged and establish a travel stop position,wherein the home stop position and the travel stop position representthe mechanical limits of travel for the lower arm, and to determineelectronic limits of travel for the lower arm based on the mechanicallimits of travel, and wherein the processor is programmed to selectivelyactivate the electric motor to move the lower arm to a desired positionbetween the electronic limits of travel, to determine stall conditionsof the lower arm based on the velocity information during movement ofthe lower arm between the electronic limits of travel, and to reversedirection of movement of the lower arm when a stall condition isdetected between the electronic limits of travel.
 12. An adjustablepedal assembly comprising, in combination: a carrier; a lower armsupported by the carrier and operatively connected to the carrier forselected movement relative to the carrier; a drive assembly operativelyconnected to the lower arm to selectively move the lower arm relative tothe carrier, the drive assembly comprising a drive screw connected toone of the lower arm and the carrier, a drive nut connected to the otherof the lower arm and the carrier and cooperating with the drive screwsuch that the drive nut travels along the drive screw upon rotation ofthe drive screw to move the lower arm, and an electric motor operativelyconnected to the drive screw to selectively rotate the drive screw; asensor positioned to detect motion information indicating movement ofthe lower arm upon rotation of the drive screw; a controller connectedto the motor to selectively activate and deactivate the motor and to thesensor to receive the motion information, the controller having aprocessor programmed to selectively activate the electric motor to movethe lower arm, to receive the motion information, and to determine stallconditions of the lower arm based on the motion information duringmovement of the lower arm; wherein the controller determines stallconditions of the lower arm during movement of the lower arm in bothforward and rearward directions; wherein the processor is programmed toreverse direction of movement of the lower arm when a stall condition isdetected between limits of travel of the lower arm: and wherein thecontroller stops movement of the lower arm when another stall conditionis detected after reversing direction of movement of the lower arm upondetecting the stall condition.